This invention relates to the removal of acetic acid from liquid ether acetates. In particular, it relates to contacting liquid ether acetates with alumina.
Ethylene glycol monobutyl ether acetate (EBA, also known as butoxyethyl acetate or butyl cellosolve acetate) is a colorless high boiling liquid which is used as a solvent for nitrocellulose lacquers, epoxy resins, multicolored lacquers, as a film coalescing aid for polyvinyl acetate latex, and for other purposes. EBA is made by reacting acetic acid with ethylene glycol monobutyl ether alcohol (EB): EQU CH.sub.3 COOH+C.sub.4 H.sub.9 OCH.sub.2 CH.sub.2 OH.fwdarw.C.sub.4 H.sub.9 OCH.sub.2 CH.sub.2 OOCH.sub.3 +H.sub.2 O.
Fractional distillation is used to separate the product from the reactants and from the water that is formed. Upon standing for a period of time hydrolysis, the reverse reaction, occurs, which contaminates the EBA with acetic acid. Commercially prepared EBA typically consists of about 98 to about 99 wt % EBA, about 1 wt % ethylene glycol monobutyl ether alcohol, and about 200 to about 1000 pmm of acetic acid. Many users of EBA require an acetic acid content of less than 200 ppm because the presence of acetic acid in EBA can cause corrosion and adherence problems and can adversely affect the properties of the inks, paints, emulsions, lacquers, etc., in which the EBA is used.
At the present time, acetic acid is removed from EBA by fractional distillation under vacuum, an expensive and time-consuming process. To reduce the acetic acid concentration, a significant amount of EBA is distilled off along with the acetic acid and the overhead EBA-acetic acid mixture must be recycled back to the synthesis step or re-distilled to recover the material. The recycling or re-distillation significantly reduces the process productivity.
Efforts have been made to stabilize EBA and prevent it from undergoing hydrolysis and forming acetic acid (see for example, EPO application No. 521,488.) U.S. Pat. application Ser. No. 08/096,395, filed Jul. 26, 1993, by Steven Qi et al. describes the addition of an amine to stabilize EBA, but the presence of an amine in EBA may be undesirable for some applications. Also, while the amine stabilizes EBA, it does not reduce the acetic acid concentration in the EBA and therefore fractional distillation of the crude EBA product is still necessary.